//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9386 SUBJECT: GRB 090518: Swift detection of a burst DATE: 09/05/18 02:09:07 GMT FROM: Scott Barthelmy at NASA/GSFC P. A. Evans (U Leicester), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), A. Rowlinson (U Leicester), M. H. Siegel (PSU), T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the Swift Team: At 01:54:44 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090518 (trigger=352420). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 119.933, +0.768 which is RA(J2000) = 07h 59m 44s Dec(J2000) = +00d 46' 04" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak with a duration of about 5 sec. The peak count rate was ~4000 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 01:55:57.8 UT, 73.5 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 119.95519, 0.75892 which is equivalent to: RA(J2000) = 07h 59m 49.25s Dec(J2000) = +00d 45' 32.1" with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 86 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (4.65e+20 cm^-2, Kalberla et al. 2005), with an excess column of 4.9 (+3.56/-2.94) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 77 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.04. Burst Advocate for this burst is P. A. Evans (pae9 AT star.le.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9387 SUBJECT: GRB 090518: Enhanced Swift-XRT position DATE: 09/05/18 08:33:11 GMT FROM: Phil Evans at U of Leicester P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 3965 s of XRT Photon Counting mode data and 8 UVOT images for GRB 090518, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 119.95404, +0.75921 which is equivalent to: RA (J2000): 07h 59m 48.97s Dec (J2000): +00d 45' 33.2" with an uncertainty of 1.6 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, arXiv:0812.3662). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9388 SUBJECT: GRB 090518: Swift-XRT refined analysis DATE: 09/05/18 09:44:36 GMT FROM: Phil Evans at U of Leicester P. A. Evans (U Leicester) reports on behalf of the Swift-XRT team: We have analysed 6.4 ks of XRT data for GRB 090518 (Evans et al. GCN Circ. 9386), from 88 s to 13.0 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN. Circ 9387). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=1.5 (+0.4, -0.3). At T+332 s the decay flattens to an alpha of 0.29 (+0.16, -0.38) before breaking again at T+2743 s to a final decay with index alpha=1.1 (+/-0.3). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.1 (+/-0.4). The best-fitting absorption column is 6.2 (+2.3, -1.9) x 10^21 cm^-2, in excess of the Galactic value of 4.6 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.9 x 10^-11 (9.9 x 10^-11) erg cm^-2 count^-1. If the light curve continues to decay with a power-law decay index of 1.1, the count rate at T+24 hours will be 0.0031 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.5 x 10^-13 (3.1 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00352420. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9389 SUBJECT: GRB090518 : Optical upper limit by MOA-II telescope DATE: 09/05/18 12:03:46 GMT FROM: Takashi Sako at Nagoya U./MOA T. Sako, A. Fukui, K. Nishimoto (STE Lab, Nagoya Univ.) on behalf of the MOA Collabration report: We searched for an optical afterglow of GRB090518 (GCN 9386, Evans et al.; GCN 9387, Evans et al.) starting from 7:02:10 UT (5 hours after the burst) with the MOA-II 1.8m telescope at Mt.John observatory in New Zealand. In a single image of a 300sec exposure with a wideband Red filter (center wavelength ~ 750nm and FWHM ~ 250nm), we did not find any object within the error circle of the Swift XRT source position (GCN 9387). A 5 sigma upper limit is set in the I magnitude at 18.9 mag. This photometry was done by using the DoPhoto and calibrated against the USNO-B1.0 catalog stars, and not corrected for the Galactic extinction. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9392 SUBJECT: GRB 090518B: Fermi GBM detection DATE: 09/05/18 14:45:29 GMT FROM: Andreas von Kienlin at MPE A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team: "At 05:51:04.67 UT on 18 May 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090518B (trigger 264318666 / 090518244). The on-ground calculated location, using the GBM trigger data, is RA = 211.2, DEC = -16.7 (J2000 degrees, equivalent to 14h 05m, -16d 42'), with an uncertainty of 4.5 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which is currently estimated to be 2 to 3 degrees). The angle from the Fermi LAT boresight is 90 degrees. The GBM light curve shows one structured peak with a duration (T90) of about 12 s (8-1000 keV). The time-averaged spectrum from T0-0.768 s to T0+6.656 s is well fit by a power law function with an exponential high energy cutoff. The power law index is -0.74 +/- 0.13 and the cutoff energy, parameterized as Epeak, is 127 +/- 12 keV (chi squared 399 for 363 d.o.f.). The event fluence (8-1000 keV) in this time interval is (2.2 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.256 s in the 8-1000 keV band is 5.6 +/- 0.6 ph/s/cm^2. The spectrum can also be fit by using a Band function with Epeak = 86 +/- 15 keV and beta = -2.10 +/- 0.14. However alpha is poorly constrained. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9393 SUBJECT: GRB 090518, Swift-BAT refined analysis DATE: 09/05/18 15:29:11 GMT FROM: Takanori Sakamoto at NASA/GSFC J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-119 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 090518 (trigger #352420) (Evans, et al., GCN Circ. 9386). The BAT ground-calculated position is RA, Dec = 119.957, 0.778 deg which is RA(J2000) = 07h 59m 49.6s Dec(J2000) = +00d 46' 41.4" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 75%. The mask-weighted light curve shows a FRED-like peak starting at T-0.5 sec, peaking at T+0 sec, and ending at T+3 sec. T90 (15-350 keV) is 6.9 +- 1.7 sec (estimated error including systematics). The time-averaged spectrum from T-2.4 to T+6.9 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.54 +- 0.14. The fluence in the 15-150 keV band is 4.7 +- 0.4 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-0.08 sec in the 15-150 keV band is 2.4 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/352420/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9394 SUBJECT: GRB 090518: P60 Observations DATE: 09/05/18 21:51:50 GMT FROM: S. Bradley Cenko at Caltech S. B. Cenko (UC Berkeley) reports on behalf of a larger collaboration: We have imaged the field of GRB090518 (Evans et al., GCN 9386) with the automated Palomar 60-inch telescope beginning at 3:45 UT on 2009 May 18 (~ 1.83 hr after the burst). Observations were taken in the r', i', and z' filters at high airmass. We find no sources inside the enhanced XRT error circle (Evans et al., GCN 9387), to the following limiting magnitudes: Filter Magnitude -------------------------------- r' > 20.5 i' > 20.0 z' > 19.0 No correction has been applied for Galactic extinction along the line of sight. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9395 SUBJECT: GRB090518: GROND upper limits DATE: 09/05/19 02:37:52 GMT FROM: Andrea Rossi at TLS Tautenburg A. Rossi (Tautenburg), P. Afonso and J. Greiner( both MPE Garching) report on behalf of the GROND team: GROND (Greiner et al. 2008, PASP 120, 405), mounted at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), observed the field of GRB 090518 (P. Evans et al. 2009, GCN #9386) simultaneously in the g'r'i'z'JHK bands. Observations started on May 18, at 23:01 UTC, 21.1 h after the burst. In stacked images of 49 min total integration time in griz and 40 min in JHK, we do not detect any new object inside the enhanced XRT error circle (P. Evans et al., GCN #9387), down to the following limiting magnitudes (all in the AB system): g' > 24.5 r' > 24.9 i' > 24.2 z' > 23.8 J > 22.4 H > 22.1 K > 21.2 The upper limits have been obtained using GROND zero points and 2MASS field stars as reference. No correction has been made for the expected extinction corresponding to E(B-V) of 0.04 mag. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9397 SUBJECT: GRB 090518: Swift/UVOT Upper Limits DATE: 09/05/19 11:50:39 GMT FROM: Frank Marshall at GSFC F.E. Marshall (NASA/GSFC) and P. Evans (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT observed the field of GRB 090518 starting 77 s after the BAT trigger (Evans et al., GCN Circ. 9386). No optical afterglow is detected in the initial UVOT exposures at the position of the X-ray afterglow (Evans et al., GCN Circ. 9387). Three-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white (FC) 77 227 147 >20.7 white 77 1367 373 >21.3 v 620 1417 97 >19.3 b 545 1341 78 >19.7 u 290 1316 304 >20.0 uvw1 669 1466 97 >19.7 uvm2 644 1442 97 >21.2 uvw2 596 1392 97 >20.0 The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.04 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9419 SUBJECT: GRB 090518: Fermi GBM detection DATE: 09/05/22 16:29:30 GMT FROM: Bill Paciesas at UAH W. Paciesas (UAH) reports on behalf of the Fermi GBM Team: "At 01:54:44.52 UT on 18 May 2009, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 090518 (trigger 264304486 / 090518080). which was also detected by the SWIFT-BAT (Evans et al. 2009, GCN 9386) The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 53 degrees. The GBM light curve consists of a single asymmetric peak with a duration (T90) of about 9 s (8-1000 keV). The time-averaged spectrum from T0-2.048 s to T0+7.04 s is adequately fit by a simple power law function with index -1.59 +/- 0.06 (chi squared 688 for 688 d.o.f.). The event fluence (8-1000 keV) in this time interval is (1.60 +/- 0.05)E-6 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.64 s in the 8-1000 keV band is 4.7 +/- 0.1 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9423 SUBJECT: GRB 090518 - NOT upper limit DATE: 09/05/26 07:21:31 GMT FROM: Johan U. Fynbo at U.Copenhagen C. C. Thoene (INAF/OAB), E. Kankare (NOT), J. P. U. Fynbo, D. Malesani (DARK/NBI), A. J. Levan (Univ. Warwick), P. Jakobsson (Univ. Iceland), J. Hjorth (DARK/NBI) report: We observed the field of GRB 090518 (GCN 9386, Evans et al.) with ALFOSC/NOT on La Palma starting May 18, 20:54 UT (21 h after the burst). Observations were obtained in R (3x300s), I (3x300s) and z (6x200s) filters at high airmass. We do not detect any new source at the XRT position (GCN 9387, Evans et al.) in the summed image of each filter. The following upper limits were obtained (based on USNO B1.0 reference stars and a NOT z-band archival zeropoint): R > 23.7 mag I > 21.8 mag z(AB) > 22.5 mag //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 9426 SUBJECT: GRB090518B optical limit by "Pi of the Sky" DATE: 09/05/27 13:54:07 GMT FROM: Marcin Sokolowski at Soltan Inst. Nuc Studies,Warsaw M.Cwiok, W.Dominik, G.Kasprowicz, A.Majcher, A.Majczyna, K.Malek, L.Mankiewicz, K.Nawrocki, L.W.Piotrowski, D.Rybka, M.Sokolowski, J.Uzycki, G.Wrochna, M.Zaremba, A.F.Zarnecki on behalf of "Pi of the Sky" collaboration http://grb.fuw.edu.pl The "Pi of the Sky" apparatus observed error box of Fermi GRB090518B before, during and after the burst, starting 23 minutes before the Fermi trigger. No new source brighter than 11 mag has been identified on 10s exposures. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10002 SUBJECT: GRB 090518: Skynet/PROMPT Observations DATE: 09/10/09 03:19:09 GMT FROM: Josh Haislip at U.North Carolina J. Haislip, D. Reichart, K. Ivarsen, A. LaCluyze, A. Foster, J. Moore, A. Oza, M. Schubel, J. Styblova, A. Trotter, J. A. Crain, and M. Nysewander report: Skynet observed the Swift/BAT localization of GRB 090518 (Evans et al., GCN 9386) with four of the 16" PROMPT telescopes at CTIO beginning 3.3 minutes after the trigger in UVRI. We do not detect the afterglow (Evans et al., GCN 9386) within the enhanced Swift/XRT localization (Evans et al., GCN 9387). Stacking only images that increase the limiting magnitude yields: mean 1-sig. 1-sig. time 3-sig. sys. stat. since lim. cal. cal. cal. trig. tel. exp. fil. mag. stars unc. unc. (m) (# x s) (mag) (mag) 5.2 PROMPT-4 4 x 40 I 18.2 229 USNO B1 0.372 0.001 + 1 x 10 5.8 PROMPT-5 2 x 40 V 18.3 72 NOMAD 0.146 0.001 6.4 PROMPT-2 1 x 80 R 19.3 217 USNO B1 0.305 0.001 + 2 x 40